Joining metal or alloy components using electric current

ABSTRACT

A system may include a current source; a first metal or alloy component with a first major surface electrically coupled to the current source; a second metal or alloy component with a second major surface electrically coupled to the current source; a metal or alloy powder disposed in at least a portion of the joint region; and a controller. The first and second major surfaces may be positioned adjacent to each other to define a joint region. The controller may be configured to cause the current source to output an alternating current that passes from the first component, through at least a portion of the metal or alloy powder, into the second component. The frequency of the alternating current may be configured to cause standing electromagnetic waves within at least a portion of the particles of the metal or alloy powder.

This application claims the benefit of U.S. Provisional Application No.62/526,274, filed Jun. 28, 2017, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The disclosure relates to systems and techniques for joining metal oralloy components using electric current.

BACKGROUND

Some articles formed from metals or alloys are more easily formed out ofmultiple parts. For example, the geometry of the article may be complexand may be difficult to form from a single piece of metal or alloy.Joining multiple metal or alloy parts may be difficult, however, as somejoining techniques may use joining material that may have undesirablemechanical properties, chemical properties, or both; require longjoining cycle times; or require prolonged exposure to elevatedtemperatures for joining.

SUMMARY

In some examples, the disclosure describes a system that includes acurrent source; a first component including a first metal or alloy and afirst major surface, where the first component is electrically coupledto the current source; a second component including a second metal oralloy and a second major surface, where the second component iselectrically coupled to the current source; a metal or alloy powder; anda controller. The first major surface of the first component and thesecond major surface of the second component may be positioned adjacentto each other to define a joint region between adjacent portions of thefirst major surface of the first component and the second major surfaceof the second component. The metal or alloy powder may be disposed in atleast a portion of the joint region. The controller may be configured tocause the current source to output an electric current that passes fromthe first component, through at least a portion of the metal or alloypowder, into the second component. The electric current may be analternating current. A frequency of the alternating current may beconfigured to cause standing electromagnetic waves within at least aportion of the particles of the metal or alloy powder.

In some examples, the disclosure describes a method that may includepositioning a first component including a first metal or alloy and afirst major surface, where the first component is electrically coupledto a current source, adjacent to a second component including a secondmetal or alloy and a second major surface, where the second component iselectrically coupled to the current source, to define a joint regionbetween adjacent portions of the first major surface of the firstcomponent and the second major surface of the second component. Themethod also may include introducing a metal or alloy powder to at leasta portion of the joint region. The method also may include controlling,by a controller, a current source to cause the current source to outputan electric current that passes from the first component, through atleast a portion of the metal or alloy powder, into the second component.The electric current may be an alternating current. A frequency of thealternating current may be configured to cause standing electromagneticwaves within at least a portion of the particles of the metal or alloypowder.

In some examples, the disclosure describes a controller that may beconfigured to pass an electric current from a current source into afirst component, through at least a portion of a metal or alloy powder,into a second component. The first component may include a first metalor alloy and a first major surface, and may be electrically coupled tothe current source. The second component may include a second metal oralloy and a second major surface, and may be electrically coupled to thecurrent source. The first major surface of the first component and thesecond major surface of the second component may be positioned adjacentto each other to define a joint region between adjacent portions of thefirst major surface of the first component and the second major surfaceof the second component. The metal or alloy powder may be disposed in atleast a portion of the joint region. The electric current may be analternating current. A frequency of the alternating current may beconfigured to cause standing electromagnetic waves within at least aportion of the particles of the metal or alloy powder.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual and schematic diagram illustrating an examplesystem for joining a first metal or alloy component and a second metalor alloy component using a metal or alloy powder by passing electriccurrent through the powder.

FIG. 2 is a flow diagram illustrating an example technique for joining afirst metal or alloy component and a second metal or alloy componentusing a metal or alloy powder by passing electric current through thepowder.

FIG. 3 is a conceptual and schematic diagram illustrating an examplesystem for joining a first metal or alloy component and a second metalor alloy component using a metal or alloy powder by passing electriccurrent in series through the first metal or alloy component to induce amagnetic field in the metal or alloy powder.

FIG. 4 is a conceptual and schematic diagram illustrating an examplesystem for joining a first metal or alloy component and a second metalor alloy component using a metal or alloy powder by passing a firstelectric current through the first metal or alloy component in a firstcurrent loop and passing a second electric current through the secondmetal or alloy component in a second current loop to induce a magneticfield in the metal or alloy powder.

FIG. 5 is a flow diagram illustrating an example technique for joining afirst metal or alloy component and a second metal or alloy componentusing a metal or alloy powder by passing electric current through thefirst metal or alloy component and the second metal or alloy componentto induce a magnetic field in the metal or alloy powder.

DETAILED DESCRIPTION

The disclosure describes systems and techniques for joining first andsecond metal or alloy components using a metal or alloy powder bypassing an electric current through the powder. In some examples, asystem for joining first and second metal or alloy components using ametal or alloy powder may include a current source electrically coupledto the first and second components and a controller. The first andsecond metal components may be positioned adjacent to each other todefine a joint region. The metal or alloy powder may be disposed in atleast a portion of the joint region and may include a metal or alloywith desirable mechanical properties, chemical properties, or both. Forexample, the metal or alloy powder may include reduced amounts ofmelting point depressants (e.g., B, Si, or the like) compared to brazealloys. Hence, joints formed using the metal or alloy powder may have ahigher melting temperature than joints formed using braze alloys, mayhave reduced brittleness compared to joints formed using braze alloys,or both.

The controller may be configured to cause the current source to outputan electric current that passes from the first component, through atleast a portion of the metal or alloy powder, and into the secondcomponent. The electric current passing through the metal or alloypowder may heat and soften or melt at least a portion of the powder. Thepowder then may be allowed to cool and solidify. In this way, thesystems and techniques of this disclosure may allow joining of metal oralloy components with a joining material having desirable mechanicalproperties, chemical properties, or both, without exposing the metal oralloy components to undesirably long cycle times or prolonged, elevatedtemperatures. Thus, the systems and techniques of the disclosure mayallow joining of metal or alloy components in a reduced amount of time,with joints that have improved mechanical strength and thermalstability, and with reduced impact on the microstructure of the metal oralloy components being joined.

FIG. 1 is a conceptual and schematic diagram illustrating an examplesystem 10 for joining a first component 12 and a second component 14using a powder 20 by passing electric current through powder 20. In someexamples, first component 12 and second component 14 may be joined toform an article or a portion of an article that is part of a hightemperature mechanical system. For example, first component 12 andsecond component 14 may be joined to form a component of a gas turbineengine, such as a gas turbine engine blade, gas turbine engine vane,blade track, combustor liner, or the like.

Each of first component 12 and second component 14 may include a metalor alloy. In some examples, each of first component 12 and secondcomponent 14 may include a Ni-, Co-, Fe-based superalloy, or Ti-basedalloy, or the like. The alloy may include other additive elements toalter its mechanical and chemical properties, such as toughness,hardness, temperature stability, corrosion resistance, oxidationresistance, and the like. Any useful alloy may be utilized in firstcomponent 12 and second component 14, including, for example, Ni-basedalloys available from Martin-Marietta Corp., Bethesda, Md., under thetrade designation MAR-M246, MAR-M247; Ni-based alloys available fromCannon-Muskegon Corp., Muskegon, Mich., under the trade designationsCMSX-3, CMSX-4, CMSX-10, and CM-186; Co-based alloys available fromMartin-Marietta Corp., Bethesda, Md., under the trade designationMAR-M509; and the like. The compositions of CMSX-3 and CMSX-4 are shownbelow in Table 1.

TABLE 1 CMSX-3 CMSX-4 (wt. %) (wt. %) Cr 8 6.5 Al 5.6 5.6 Ti 1 1 Co 5 10W 8 6 Mo 0.6 0.6 Ta 6 6 Hf 0.1 0.1 Re — 3 Ni Balance Balance

In some examples, first component 12 and second component 14 includesubstantially the same (e.g., the same or nearly the same) metal oralloy. In other examples, first component 12 and second component 14include different metals or alloys. For example, first component 12 mayinclude a first alloy and second component 14 may include a second,different alloy, the first alloy providing a greater mechanical strengthcompared to the second alloy, and the second alloy providing a greaterthermal resistance compared to the first alloy. In this way, the firstcomponent 12 and the second component 14 may exhibit differentmechanical properties, chemical properties, or both.

Each of first component 12 and second component 14 may be made using atleast one of casting, forging, powder metallurgy, or additivemanufacturing. In some examples, first component 12 and second component14 are made using the same process, while in other examples, firstcomponent 12 and second component 14 are made using different processes.

Although FIG. 1 illustrates first component 12 and second component 14as each defining a simple, substantially rectangular geometry, in otherexamples, first component 12, second component 14, or both may define amore complex geometry, including simple or complex curves, overhangs,undercuts, internal cavities, or the like.

First component 12 defines at least one joint surface 16. Similarly,second component 14 defines at least one joint surface 18. In someexamples, joint surfaces 16 and 18 may define complementary shapes. FIG.1 illustrates joint surfaces 16 and 18 as substantially flat surfaces.In other examples, joint surfaces 16 and 18 may define other, morecomplex complementary shapes, including, for example, simple or complexcurves, overhangs, undercuts, apertures, annuluses, or the like.

First component 12 and second component 14 are positioned such thatjoint surfaces 16 and 18 are adjacent to each other and define a jointregion 22. Joint region 22 may include any kind of simple or complexjoint, including, for example, at least one of a bridle joint, a buttjoint, a miter joint, a dado joint, a groove joint, a tongue and groovejoint, a mortise and tenon joint, a birdsmouth joint, a halved joint, abiscuit joint, a lap joint, a double lap joint, a dovetail joint, asplice joint, or the like. Consequently, joint surfaces 16 and 18 mayhave any corresponding geometries to define the surfaces of the jointregion 22. For example, for a mortise and tenon joint, first component12 may define a mortise (a cavity) and second component 14 may define atenon (a projection that inserts into the mortise). As another example,for a splice joint, first component 12 may define a half lap, a bevellap, or the like, and second component 14 may define a complementaryhalf lap, bevel lap, or the like.

In some examples, although not shown in FIG. 1, system 10 may include aclamp, press, or other mechanism for exerting pressure between firstjoint surface 16 and second joint surface 18 during the joiningtechnique. The pressure between first joint surface 16 and second jointsurface 18 may facilitate formation of the joint, for example, byhelping to at least one of maintain the gap of joint region 22, promoteflow of powder 20, or evacuate any gases or porosity in powder 20, whichreduces porosity in the joint.

Disposed in joint region 22 is a powder 20. Powder 20 may include ametal or alloy. For example, powder 20 may include may include a Ni-,Co-, or Fe-based superalloy powder, or Ti-based alloy powder, or thelike. The alloy of powder 20 may include other additive elements toalter mechanical properties, chemical properties, or both, of the alloy,such as toughness, hardness, temperature stability, corrosionresistance, oxidation resistance, or the like. Any useful alloy powdermay be utilized in powder 20. For example, powder 20 may possesssufficient mechanical strength and high temperature oxidation resistanceto be used in a component in a gas turbine engine. In some examples,powder 20 may include alloys such as, for example, Inconel 718, Rene 88,Udimet 720, or the like, or elemental metals such as, for example,titanium, vanadium, zirconium, or the like.

In some examples, powder 20 may include substantially the samecomposition as one or both of first component 12 or second component 14,or a composition that includes a blend of the composition of firstcomponent 12 and the composition of second component 14 (e.g., inexamples in which first component 12 and second component 14 are formedof different alloys). Selecting a composition of powder 20 that issubstantially the same as the composition of first component 12, secondcomponent 14, or both may improve bonding to the respective component.Selecting a composition of powder 20 that is a blend of the compositionof first component 12 and second component 14 may improve bonding toboth components, e.g., compared to a dissimilar composition of powder20.

In some examples, powder 20 may be substantially free of a melting pointdepressant. For example, powder 20 may be substantially free of boron,silicon, or both. Selecting a composition of powder 20 that issubstantially free of boron, silicon, or both may improve the mechanicalproperties, chemical properties, or both, of the joint.

In some examples, metal or alloy powder 20 may have a selected powdermesh size, and may be produced by induction melting the metal or alloy,respectively, in vacuum or an argon atmosphere, followed by argon gasatomization. Each individual powder component used in powder 20 may beanalyzed to confirm the particle size and chemical composition.

In some examples, joint region 22 may define a joint thickness (e.g.,the gap between joint surface 16 of first component 12 and joint surface18 of second component 14 in a direction normal to joint surfaces 16 and18). In some example, the joint thickness may be substantially similar(e.g., the same or nearly the same) across the joint area (e.g., thesurface area defined by one or both of joint surfaces 16 and 18). Inother examples, the joint thickness may differ across the joint area. Insome examples, the joint thickness may be less than or equal to about127 micrometers (about 0.005 inch). In some examples, the jointthickness may define a thinner thickness, such as about 51 micrometers(about 0.002 inch). In other examples, joint thickness may define agreater thickness, such as up to about 1524 micrometers (about 0.060inch), or about 1016 micrometers (about 0.040 inch).

By utilizing powder 20, metals or alloys with desirable mechanicalproperties and/or chemical properties (e.g., high temperature oxidationresistance, tensile strength, high temperature creep resistance, thermalcycling fatigue resistance, or the like) may be utilized in a joiningtechnique to join first component 12 and second component 14. Theresulting joint may possess sufficient mechanical properties and/orchemical properties to be utilized in a high temperature mechanicalsystem, such as a component in a gas turbine engine. For example, powder20 may include reduced amounts of melting point depressants (e.g., B,Si, or the like) compared to braze alloys. Hence, joints formed usingpowder 20 may have a higher melting temperature than joints formed usingbraze alloys, may have reduced brittleness compared to joints formedusing braze alloys, or both. In this way, powder 20 may facilitatejoining components used in a high temperature mechanical system, whichmay allow formation of an article from multiple, smaller components,easing, or reducing the cost of manufacturing the article.

Current source 24 may be electrically coupled to first component 12 byfirst connection 28 and second component 14 by second connection 30.First and second connections 28 and 30 may include any suitable materialfor conducting electric current from current source 24 to firstcomponent 12 or from second component 14 to current source 24 (e.g., toground). For example, first and second connections 28 and 30 may includea conductive metal, such as, for example, copper.

In some examples, first and second connections 28 and 30 may includefirst and second electrodes 32 and 34, respectively. First and secondelectrodes 32 and 34 may include any suitable material for transmittingelectric current from first connection 28 to first component 12 or fromsecond component 14 to second connection 30. For example, the first andsecond electrodes 28 and 30 may include non-consumable electrodes, suchas, for example, carbon; metals such as, for example, copper, silver,nickel, or the like; or alloys of such materials; or the like.

In some examples, at least one of first or second electrode 32 or 34 maybe configured to pass the electric current through a surface areagreater than about 16 square millimeters (mm²) on first joint surface16, second joint surface 18, or both. For example, at least one of firstor second electrode 32 or 34 may include first or second tip 36 or 38having a surface area greater than about 16 mm², such as, for example,greater than about 25 mm², greater than about 100 mm², or greater thanabout 1000 mm². In some examples, increasing the surface area of firstor second tip 36 or 38 may require increasing the amperage delivered bycurrent source 24. In this way, system 10 may pass electric currentthrough a region of powder 20 having a surface area greater than about16 mm² to enable formation of larger continuous joints compared to otherjoining techniques, such as, for example, spot welding. This may allowthe joint to have increased mechanical strength, e.g., due to increasedjoining area, may reduce a time used to join first and second components12 and 14, may allow the production of larger and/or less expensivecomponents by joining shapes in an additive manner, making the startingshape near-net shape, or the like.

In some examples, first and second electrodes 32 and 34 may beconfigured to selectively and releasably electrically couple to firstcomponent 12 and second component 14, respectively. For example,positioning of first and second electrodes 32 and 34 may be controlledmanually or by controller 26 in an automated process, e.g., usingrobotic arms. In this way, system 10 may control the position ofelectric current that passes through powder 20 such that system 10 maybe configured to pass electric current through powder 20 in multiplelocations in rapid succession to join areas larger than the area throughwhich electric current may pass in a single location of first and secondelectrodes 32 and 34.

Current source 24 may include any suitable current type. For example,current source 24 may include an alternating current source or a directcurrent source. For brevity, the flow of electrons from current source24 is described as originating from current source 24 and flowing intofirst component 12, through powder 20, into second component 14, andback to current source 24 (e.g., to ground). Other paths for the flow ofelectrons are contemplated and are not outside of the scope of thedisclose subject matter.

Current source 24 may be configured to controllably output an electriccurrent of any suitable power, voltage, and/or amperage. For example,current source 24 may be configured to output a frequency, power,voltage, and/or amperage sufficient to soften or melt at least a portionof powder 20. In some examples, current source 24 may include a switchor another current interrupter device to interrupt the flow of electronsfrom current source 24 to first component 12. In this way, the flow ofelectrons may be turned on and off. In some examples, current source 24may include a voltage controller and/or an amperage controller. In thisway, the output power level of current source 24 may be controlled. Insome examples, current source 24 may include a frequency converterand/or a waveform generator. In this way, the output frequency andwaveform of current source 24 may be controlled. For example, currentsource 24 may be configured to output direct current in a pulsedwaveform of interleaved on and off periods.

Controller 26 may be configured to cause current source 24 to output anelectric current that passes from first component 12, through at least aportion of powder 20, into second component 14. In some examples,controller 26 may be configured to control the power level output fromcurrent source 24. For example, controller 26 may control a voltageoutput and/or an amperage output from current source 24 to firstcomponent 12. In some examples, controller 26 may apply to powder 20electric current with a power sufficient to soften or melt at least aportion of powder 20.

In some examples, controller 26 may be configured to control a length oftime current is applied to powder 20. For example, controller 26 maycontrol a switch or other device to interrupt the flow of electrons fromcurrent source 24 to first component 12. In some examples, controller 26may apply electric current to powder 20 for a length of time in therange of 1 millisecond to 60 minutes. In some examples, the length oftime electric current is applied to powder 20 may be based on thecomposition of powder 20, the joint thickness, the composition of firstor second components 12 and 14, the desired heating and cooling rate, orthe power, voltage, and/or amperage of current source 24.

In the example of current source 24 that includes an alternating currentsource, current source 24 may operate at any suitable frequency. Forexample, current source 24 that includes an alternating current sourcemay operate at between about 1 hertz (Hz) to about 1 THz, for example,between about 1 MHz to about 300 GHz or between about 100 MHz to about10 GHz. In some examples, controller 26 may be configured to control afrequency or waveform of the current output from current source 24. Forexample, controller 26 may control a waveform generator and/or afrequency converter. A frequency converter may be used to control thefrequency of an alternative current output from current source 24. Awaveform generator may be used to control the waveform (e.g.,electromagnetic wave shape) of the alternating current output fromcurrent source 24. The waveform may be sinusoidal, square,sawtooth-shaped, or more complex to achieve the desired heating effect.

In some examples, the frequency of the alternating current may beconfigured to cause standing electromagnetic waves within at least aportion of the particles of powder 20.

In some examples, the average particle size of powder 20 may be selectedto provide desirable mechanical properties, chemical properties, orboth, during heating. For example, the average particle size of powder20 may be selected to heat faster at a certain frequency. In otherexample, the frequency can be selected to heat powder 20 having aparticular average particle size more quickly than a powder 20 having adifferent average particle size.

In some example, the powder packing density may affect electricalconductivity of powder 20. For example, a more densely packed powder mayhave a greater electrical conductivity compared to a less densely packedpowder. In some examples, the electrical conductivity of powder 20 mayaffect the rate at which powder 20 is heated.

In some examples, powder 20 may have a greater electrical resistivitycompared to first component 12 and second component 14. In examples inwhich powder 20 has a greater electrical resistivity than firstcomponent 12 and second component 14, resistive heating may be at leastpartially restricted to joint region 22. In other examples in whichpowder 20 has a greater electrical resistivity than first component 12and second component 14, resistive heating may be substantiallyrestricted to joint region 22.

In this way, system 10 may be used to produce a joint having desirablemechanical and chemical properties without exposing first or secondcomponents 12 and 14 to undesirably long cycle times or prolonged,elevated temperatures. For example, selection of powder 20 may include ametal or alloy with desirable mechanical properties, chemicalproperties, or both, e.g., powder 20 may include reduced amounts ofmelting point depressants (e.g., B, Si, or the like) compared to brazealloys, to produce a joint with a higher melting temperature, reducedbrittleness, or both, compared to joints formed using braze alloys orbrazing techniques. As another example, using an alternating currentthat produces resonating or standing electromagnetic waves in at least aportion of powder 20 to soften or melt at least a portion of powder 20may allow joining of first and second components 12 and 14 using powder20 in a reduced amount of time, the resulting joint having improvedmechanical strength and thermal stability, and with reduced impact onthe microstructure of first and second components 12 and 14.

FIG. 2 is a flow diagram illustrating an example technique for joining afirst metal or alloy component and a second metal or alloy componentusing a metal or alloy powder by passing electric current through thepowder. The technique of FIG. 2 will be described with reference tosystem 10 of FIG. 1 for purposes of illustration only. It will beappreciated that the technique of FIG. 2 may be performed with adifferent system, or that system 10 may be used in a different joiningtechnique.

Although not shown in FIG. 2, in some examples, prior to positioningfirst component 12 and second component 14 to define joint region 22(42), at least one of first joint surface 16 and second joint surface 18of first and second component 12 and 14, respectively, may be inspectedand cleaned. Inspecting joint surfaces 16 and 18 may include, forexample, visual inspection by a technician, automated inspection using acamera and image recognition and analysis software, e.g., implemented bycontroller 26. In response to determining that joint surfaces 16 or 18or both include contaminants, joint surfaces 16 and 18 may be cleaned,e.g., using mechanical or chemical means. For example, joint surfaces 16may be scrubbed, polished, exposed to a cleaning solvent or etchant, orthe like. Cleaning first and second joint surfaces 16 and 18 may removeparticles or other contaminants that may weaken the joint or react withthe first or second components 12 or 14 or powder 20 during the joiningtechnique or after joining (e.g., during thermal cycling or operation ofthe article including the joint). In this way, cleaned joint surfaces 16and 18 may produce a stronger joint than uncleaned joint surfaces 16 and18.

The technique of FIG. 2 includes positioning first and second components12 and 14 to define joint region 22 (42). For example, as shown in FIG.1, first and second components 12 and 14 may be positioned so that jointsurfaces 16 and 18 are near each other. In some examples, controller 26may be configured to control the positioning of first and secondcomponents 12 and 14. For example, controller 26 may control roboticcomponents to position first and second components 12 and 14, maydetermine a position of first component 12 relative to second component14 to define a desired joint region 22, or both. As described above, thegeometry of joint region 22 may depend on the type of joint defined byjoint surfaces 16 and 18 and may include, for example, a bridle joint, abutt joint, a scarf joint, a miter joint, a dado joint, a groove joint,a tongue and groove joint, a mortise and tenon joint, a birdsmouthjoint, a halved joint, a biscuit joint, a lap joint, a double lap joint,a dovetail joint, or a splice joint. As described above, joint region 22may define a joint thickness that may be substantially similar or maydiffer across the joint area, e.g., the joint thickness may be betweenabout 51 micrometers (about 0.002 inch) and about 1524 micrometers(about 0.060 inch). In this way, the technique of FIG. 2 may be used tocontrol the size and shape of joint region 22.

The technique of FIG. 2 also includes disposing metal or alloy powder 20in joint region 22 (44). For example, controller 26 may be configured tocontrol a nozzle of a powder delivery system to dispose powder 20 injoint region 22. In some examples, controller 26 may be configured toposition a nozzle of a powder delivery system in or near a portion ofjoint region 22 and controllably inject or spray powder 20 into aportion of joint region 22. In some examples, powder 20 may be disposedin joint region 22 such that powder 20 contacts substantially the entiresurface area of joint surfaces 16 and 18 (e.g., the entire surface areaor nearly the entire surface area). In other examples, powder 20 may bedisposed in joint region 22 such that powder 20 contacts only a portionof the total surface area of one or both of joint surfaces 16 and 18. Insome examples, a clamp, press, or other mechanism may be used tocompress powder 20 between joint surfaces 16 and 18 to cause intimatecontact between joint surfaces 16 and 18 and powder 20. In this way, thetechnique of FIG. 2 may be used to control the porosity and/ormechanical strength of the resulting joint.

The technique of FIG. 2 further includes passing electric currentthrough powder 20 to soften or melt at least portion of powder 20 (46).For example, controller 26 may cause current source 24 to output anelectric current, which is conducted to first component 12 via firstconnector 28 and first electrode 32. The electric current conductsthrough first component 12 to powder 20, and from powder to secondcomponent 14. In some examples, system 10 may be enclosed in a vacuum orsubstantially inert atmosphere while electric current is passed throughpowder 20 (e.g., an atmosphere including constituents that substantiallydo not react with first and second components 12 and 14 and powder 20 atthe temperatures and pressures experienced by first and secondcomponents 12 and 14 and powder 20 during the technique). In someexamples, passing electric current through powder 20 may heat at least aportion of powder 20. In some examples, the heating may be caused inwhole or in part by resistive heating of at least a portion of theparticles of powder 20. In other examples, the heating may be caused inwhole or in part by the formation of standing electromagnetic waves inat least a portion of the particles of powder 20 or by an at leastpartial resonance of the alternating current in at least a portion ofthe particles of powder 20. In other examples, the heating may be causedby the combined effect of resistive heating and resonance of thealternating current in at least a portion of the particles of powder 20.In some examples, controller 26 may control the heating by, for example,by varying the voltage, amperage, frequency, waveform, or the like ofthe electric current. In this way, the technique of FIG. 2 may useelectric current to controllably soften or melt at least a portion ofpowder 20.

In some examples, controller 26 may cause current source 24 to output anelectric signal with a selected voltage, amperage, frequency, waveform,or the like to heat at least a portion of powder 20 to the melting pointtemperature of powder 20 or a temperature near or above the meltingpoint temperature of powder 20. For example, heating at least a portionof powder 20 may include heating at least a portion of powder 20 tobetween about 188° C. and about 3500° C., or between about 600° C. andabout 1600° C., or between about 900° C. and about 1550° C.

In some examples, controller 26 may cause current source 24 to outputelectric current for a selected duration. In this way, controller 26 maycontrol the duration for which powder 20 is heated. For example, powder20 may be heated to the melting point temperature of powder 20 (or nearor above the melting point temperature of powder 20) for a time periodin the range of about 0.001 seconds to about 60 minutes, for example,between about 1 second to 5 minutes or between about 10 seconds to about2 minutes.

The technique of FIG. 2 further includes cooling softened or meltedpowder 20 to a temperature below the melting point temperature of powder20, e.g., an ambient temperature, to form a solid and join first andsecond components 12 and 14 (48). For example, controller 26 may causecurrent source 24 to stop outputting electric current, thereby allowingsoftened or melted powder 20 to cool under ambient conditions. In someexamples, controller 26 may cause current source 24 to graduallydecrease electrical current to cool the joint at a controlled rate. Insome examples, powder 20 may be cooled in a vacuum or under flowinginert gas to about 65° C. or less. In this way, the technique of FIG. 2may be used to produce a joint, i.e., joint region 22 defined by jointsurfaces 16 and 18 of first and second components, respectively, thatincludes the solidified metal or alloy of powder 20.

The technique of FIG. 2 may be used to produce a joint having desirablemechanical and chemical properties without exposing first or secondcomponents 12 and 14 to undesirably long cycle times or prolonged,elevated temperatures. For example, selection of powder 20 may include ametal or alloy with desirable mechanical properties, chemicalproperties, or both, e.g., powder 20 may include reduced amounts ofmelting point depressants (e.g., B, Si, or the like) compared to brazealloys, to produce a joint with a higher melting temperature and reducedbrittleness compared to joints formed using braze alloys or brazingtechniques. As another example, using an alternating current thatproduces resonating or standing electromagnetic waves in at least aportion of powder 20 to soften or melt at least a portion of powder 20may allow joining of first and second components 12 and 14 using powder20 in a reduced amount of time, the resulting joint having improvedmechanical strength and thermal stability, and with reduced impact onthe microstructure of first and second components 12 and 14.

In some examples, rather than a current source 24 conducting electricalcurrent through a powder to cause standing waves in the powder, a systemmay include a current source electrically connected to metal or alloycomponents in such a way that the current conducts through the metal oralloy components and induces eddy currents in a powder. For example,FIG. 3 is a conceptual and schematic diagram illustrating an examplesystem 50 for joining a first metal or alloy component 52 and a secondmetal or alloy component 54 using a metal or alloy powder 60 by passingelectric current in series through the first metal or alloy component 52and then the second metal or alloy component 54 to induce a magneticfield in the metal or alloy powder 60. System 50 may include first metalor alloy component 52 having first major surface 56 and second metal orally component 54 having second major surface 58. First major surface 56and second major surface 58 may be positioned adjacent to each other todefine joint region 62 between adjacent portions of the first majorsurface 56 and second major surface 58. Metal or alloy powder 60 may bedisposed in at least a portion of joint region 62. Each of first metalor alloy component 52, second metal or alloy component 54, and metal oralloy powder 60 may be similar to or substantially correspondingcomponent of system 10, aside from the differences described herein.

Controller 66 may control current source 64. First connection 68 andfirst electrode 72 with tip 76 may electrically couple first metal oralloy component 52 to current source 64, second connection 70 and secondelectrode 74 with tip 78 may electrically couple second metal or alloycomponent 54 to current source 64, and external electrical conductor 80may electrically couple first component 52 to second metal or alloycomponent 54.

Rather than controller 26 being configured to cause current source 24 tooutput an electric current that passes from first component 12, throughat least a portion of powder 20, into second component 14, controller 66may be configured to cause current source 64 to output an electriccurrent that passes through first metal or alloy component 52 adjacentto at least a first portion of the joint region 62, from first metal oralloy component 52 to second metal or alloy component 54 via externalelectrical conductor 80, and through second metal or alloy component 54adjacent to at least the first portion of the joint region 62.

In some examples, controller 66 may be configured to cause currentsource 64 to output a high frequency alternating current. As the highfrequency alternating current conducts through first metal or alloycomponent 52 and second metal or alloy component 54 adjacent to thefirst portion of joint region 62, the high frequency alternating currentmay induce magnetic eddy currents, magnetic hysteresis, or both, withinat least a portion of metal or alloy powder 60. The characteristics ofthe high frequency alternating current, including the current amplitude,frequency, and signal duration may be selected to be sufficient tosoften or melt at least a portion of metal or alloy powder 60 disposedin at least the first portion of joint region 62. For example, the highfrequency alternating current passing through first metal or alloycomponent 52 adjacent to at least a first portion of the joint region 62and passing through second metal or alloy component 54 adjacent to atleast the first portion of the joint region 62 may cause an alternatingmagnetic field that penetrates at least a portion of metal or alloypowder 60 disposed in at least the first portion of joint region 62. Thealternating magnetic field may cause electric currents, e.g., magneticeddy currents, in at least the portion of metal or alloy powder 60disposed in at least the first portion of joint region 62. The electriccurrents may heat metal or alloy powder 60 by Joule heating, e.g., byinteractions of the moving particles (e.g., electrons) and atomic ionsin metal or alloy powder 60.

In examples in which metal or alloy powder 60 may include at least somemagnetic material, in addition to magnetic eddy currents, thealternating magnetic field may cause magnetic hysteresis. Magnetichysteresis may cause hysteresis loss due to the irreversiblemagnetization in the magnetic field. For example, the alternatingmagnetic field applied in a first direction may cause the atomic dipolesof atoms of metal or alloy powder 60 to align with the alternatingmagnetic field. When the alternating magnetic field is reversed in asecond, opposite direction, the magnetic flux density may decrease at afirst nonlinear rate. When the field is again reversed in the firstdirection, the magnetic flux density may increase at a second, differentnonlinear rate. The difference in the first rate and second rate maygenerate a hysteresis loop. The area of the hysteresis loop may define ahysteresis loss, e.g., power loss. The hysteresis loss may heat metal oralloy powder 60. In some examples, the alternating current amplitude andfrequency may affect hysteresis loss. For example, hysteresis loss mayincrease for a greater amplitude compared to a lesser amplitude. Asanother example, hysteresis loss may increase for a lesser frequencycompared to a greater frequency.

In some examples, the frequency of the alternating current may beselected based on the size (e.g., area, depth, or volume) of jointregion 62; composition of any one of first metal or alloy component 52,second metal or alloy component 54, or metal or alloy powder 60;resistivity of metal or alloy powder 60, desired magnetic fieldpenetration depth, or the like.

In this way, system 50 may be used to produce a joint having desirablemechanical and chemical properties without exposing first or secondmetal or alloy components 52 and 54 to undesirably long cycle times orprolonged, elevated temperatures. For example, selection of metal oralloy powder 60 may include a metal or alloy with desirable mechanicalproperties, chemical properties, or both, e.g., metal or alloy powder 60may include reduced amounts of melting point depressants (e.g., B, Si,or the like) compared to braze alloys, to produce a joint with a highermelting temperature, reduced brittleness, or both, compared to jointsformed using braze alloys or brazing techniques. As another example,using an alternating current that induces magnetic eddy currents,magnetic hysteresis, or both in at least a portion of metal or alloypowder 60 to soften or melt at least a portion of metal or alloy powder60 may allow joining of first and second metal or alloy components 52and 54 using metal or alloy powder 60 in a reduced amount of time, theresulting joint having improved mechanical strength and thermalstability, and with reduced impact on the microstructure of first andsecond metal or alloy components 52 and 54.

FIG. 4 is a conceptual and schematic diagram illustrating anotherexample system for joining a first metal or alloy component and a secondmetal or alloy component using a metal or alloy powder by passing afirst electric current through the first metal or alloy component in afirst current loop and passing a second electric current through thesecond metal or alloy component in a second current loop to induce amagnetic field in the metal or alloy powder. In some examples, system 90may include a first metal or alloy component 92 having first majorsurface 96 and a second metal or alloy component 94 having second majorsurface 98. First major surface 96 and second major surface 98 may bepositioned adjacent to each other to define joint region 102 betweenadjacent portions of the first major surface 96 and second major surface98. Metal or alloy powder 100 may be disposed in at least a portion ofjoint region 102. Each component of system 90 may be similar orsubstantially the same as the corresponding component of system 50,aside from the differences described herein.

In some examples, first controller 106 controls first current source104. First connection 108 and first electrode 112 with tip 116electrically couple first metal or alloy component 92 to first currentsource 104 at first position 113, and second connection 110 and secondelectrode 114 with tip 118 electrically couple first metal or alloycomponent 92 to first current source 104 at a second, different position115.

In some examples, second controller 126 controls second current source124. In some examples, third connection 128 and third electrode 132 withtip 136 may electrically couple second metal or alloy component 94 tosecond current source 124 at a third position 133, and fourth connection130 and fourth electrode 134 with tip 138 may electrically couple secondmetal or alloy component 94 to second current source 104 at a fourth,different position 135. In other examples, a single controller maycontrol both first current source 104 and second current source 124,first and second current sources 104 and 124 may be combined and outputan electrical signal to first connection 108 and third connection 128 inparallel, or both.

Rather than controller 66 being configured to cause current source 64 tooutput an electric current that passes through first component 52adjacent to at least a first portion of the joint region 62 from firstcomponent 52 to second component 54 via an external electrical conductor80 and through second component 54 adjacent to at least the firstportion of the joint region 62, first controller 106 may be configuredto cause first current source 104 to output a first high frequencyalternating current that passes from first position 113, through firstmetal or alloy component 92 adjacent to at least a first portion ofjoint region 102, and to second position 115. Similarly, secondcontroller 126 may be configured to cause second current source 124 tooutput a second high frequency alternating current that passes fromthird position 133, through second metal or alloy component 94 adjacentto at least the first portion of joint region 102, to fourth position135.

In some examples, controllers 106 and 126 may be configured to causecurrent sources 104 and 124 to output a first and second high frequencyalternating current that may induce magnetic eddy currents, magnetichysteresis, or both, within at least a portion of metal or alloy powder100 sufficient to soften or melt at least a portion of powder 100disposed in at least the first portion of the joint region 102. Forexample, the first high frequency alternating current passing throughfirst metal or alloy component 92 adjacent to at least a first portionof the joint region 102 and the second high frequency alternatingcurrent passing through second metal or alloy component 94 adjacent toat least the first portion of the joint region 102 may cause analternating magnetic field that penetrates at least a portion of metalor alloy powder 100 disposed in at least the first portion of the jointregion 102 to cause magnetic eddy currents, magnetic hysteresis, or bothin at least a portion of metal or alloy powder 100 disposed in at leastthe first portion of the joint region 102.

In this way, system 90 may be used to produce a joint having desirablemechanical and chemical properties without exposing first or secondmetal or alloy components 92 and 94 to undesirably long cycle times orprolonged, elevated temperatures. For example, selection of metal oralloy powder 100 may include a metal or alloy with desirable mechanicalproperties, chemical properties, or both, e.g., metal or alloy powder100 may include reduced amounts of melting point depressants (e.g., B,Si, or the like) compared to braze alloys, to produce a joint with ahigher melting temperature, reduced brittleness, or both, compared tojoints formed using braze alloys or brazing techniques. As anotherexample, using an alternating current that induces magnetic eddycurrents, magnetic hysteresis, or both in at least a portion of metal oralloy powder 100 to soften or melt at least a portion of metal or alloypowder 100 may allow joining of first and second metal or alloycomponents 92 and 94 using metal or alloy powder 100 in a reduced amountof time, the resulting joint having improved mechanical strength andthermal stability, and with reduced impact on the microstructure offirst and second metal or alloy components 92 and 94.

FIG. 5 is a flow diagram illustrating an example technique for joining afirst metal or alloy component and a second metal or alloy componentusing a metal or alloy powder by passing electric current through thefirst metal or alloy component and the second metal or alloy componentto induce a magnetic field in the powder. The technique of FIG. 5 willbe described with reference to system 50 of FIG. 3 and system 90 of FIG.4 for purposes of illustration only. It will be appreciated that thetechnique of FIG. 5 may be performed with a different system, or thatsystem 50 or system 90 may be used in a different joining technique.

Each step of the technique of FIG. 5 may be similar or substantially thesame as the corresponding step in the technique of FIG. 2, aside fromthe differences described herein. The technique of FIG. 5 includespositioning first metal or alloy component 52 adjacent to second metalor alloy component 54 to define joint region 62 (142). The technique ofFIG. 5 also includes disposing metal or alloy powder 60 in joint region62 (144). Rather than passing electric current through powder 20 tosoften or melt at least portion of powder 20 (46), the technique of FIG.5 may include, with reference to FIG. 3, passing electric currentthrough first metal or alloy component 52 and second metal or alloycomponent 54 to induce a magnetic field in metal or alloy powder 60 tosoften or melt at least a portion of metal or alloy powder 60 (146). Forexample, controller 66 may be configured to cause current source 64 tooutput an electric current that passes through first metal or alloycomponent 52 adjacent to at least a first portion of the joint region62, from first component 52 to second metal or alloy component 54 via anexternal electrical conductor 80, and through second metal or alloycomponent 54 adjacent to at least the first portion of the joint region62 to induce magnetic eddy currents, magnetic hysteresis, or both,within at least a portion of metal or alloy powder 60 sufficient tosoften or melt at least a portion of metal or alloy powder 60 disposedin at least the first portion of the joint region 62. In some examples,the induced magnetic eddy currents, magnetic hysteresis, or both, withinmetal or alloy powder 60 may heat at least a portion of metal or alloypowder 60. In some examples, controller 66 may control the heating by,for example, by controlling the voltage, amperage, frequency, waveform,duration, or the like of the electric current. In this way, thetechnique of FIG. 5 may use electric current to controllably soften ormelt at least a portion of metal or alloy powder 60.

As another example, with reference to FIG. 4, first controller 106 maybe configured to cause first current source 104 to output a first highfrequency alternating current that passes from first position 113,through first metal or alloy component 92 adjacent to at least a firstportion of joint region 102, and to second position 115, and secondcontroller 126 may be configured to cause first current source 124 tooutput a second high frequency alternating current passes from thirdposition 133, through second metal or alloy component 94 adjacent to atleast the first portion of joint region 102, to fourth position 135 toinduce magnetic eddy currents, magnetic hysteresis, or both, within atleast a portion of metal or alloy powder 100. The magnetic eddycurrents, magnetic hysteresis, or both, may be sufficient to soften ormelt at least a portion of metal or alloy powder 100 disposed in atleast the first portion of the joint region 102. In some examples, theinduced magnetic eddy currents, magnetic hysteresis, or both, withinmetal or alloy powder 100, may heat at least a portion of metal or alloypowder 100. In some examples, first controller 106 and/or secondcontroller 126 may control the heating by, for example, by varying thevoltage, amperage, frequency, waveform, or the like of the first orsecond electric current. In this way, the technique of FIG. 5 may useelectric current to controllably soften or melt at least a portion ofmetal or alloy powder 100.

The technique of FIG. 5 further includes cooling softened or meltedmetal or alloy powder 60 to a temperature below the melting pointtemperature of metal or alloy powder 60, e.g., an ambient temperature,to form a solid and join first and second metal or alloy components 52and 54 (148)

The functions described herein may be implemented in hardware, software,firmware, or any combination thereof. If implemented in software, thefunctions may be stored on or transmitted over, as one or moreinstructions or code, a computer-readable medium or computer-readablestorage device and executed by a hardware-based processing unit.Computer-readable media may include computer-readable storage media,which corresponds to a tangible medium such as data storage media, orcommunication media including any medium that facilitates transfer of acomputer program from one place to another, e.g., according to acommunication protocol. In this manner, computer-readable mediagenerally may correspond to (1) tangible computer-readable storage mediaor computer-readable storage device, which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can include RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transient media, but areinstead directed to non-transient, tangible storage media. Disk anddisc, as used herein, include compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules. Also, the techniques couldbe fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including an integrated circuit (IC) or a setof ICs (e.g., a chip set). Various components, modules, or units aredescribed in this disclosure to emphasize functional aspects of devicesconfigured to perform the disclosed techniques, but do not necessarilyrequire realization by different hardware units. Rather, as describedabove, various units may be combined in a hardware unit or provided by acollection of interoperative hardware units, including one or moreprocessors as described above, in conjunction with suitable softwareand/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A system comprising: a current source; a firstcomponent comprising a first metal or alloy and a first major surface,wherein the first component is electrically coupled to the currentsource; a second component comprising a second metal or alloy and asecond major surface, wherein the second component is electricallycoupled to the current source, wherein the first major surface of thefirst component and the second major surface of the second component arepositioned adjacent to each other to define a joint region betweenadjacent portions of the first major surface of the first component andthe second major surface of the second component; a metal or alloypowder disposed in at least a portion of the joint region; a controllerconfigured to cause the current source to output an electric currentthat passes from the first component, through at least a portion of themetal or alloy powder, into the second component, wherein: the electriccurrent is an alternating current, and the frequency of the alternatingcurrent is configured to cause standing electromagnetic waves within atleast a portion of the particles of the metal or alloy powder.
 2. Thesystem of claim 1, further comprising a first electrode electricallycoupled to the current source and the first component and a secondelectrode electrically coupled to the current source and the secondcomponent, wherein the controller is further configured to controlpositions of the first electrode and the second electrode relative tothe first and second components, respectively.
 3. The system of claim 2,wherein at least one of the first electrode or the second electrode isconfigured to pass the alternating current through a surface areagreater than about sixteen square millimeters on the first major surfaceor the second major surface.
 4. The system of claim 1, wherein thefrequency of the alternating current is between about 1 kHz to about 10GHz.
 5. The system of claim 1, wherein the first metal or alloy isdifferent than the second metal or alloy.
 6. The system of claim 1,wherein at least one of the first component and the second componentcomprises a nickel based superalloy or a titanium based alloy.
 7. Thesystem of claim 1, wherein the metal or alloy powder comprisessubstantially the same composition as the first component, substantiallythe same composition as the second component, or a compositioncomprising a blend of the composition of the first component and thecomposition of the second component.
 8. The system of claim 1, whereinthe metal or alloy powder is substantially free of a melting pointdepressant.
 9. A method comprising: positioning a first componentcomprising a first metal or alloy and a first major surface, wherein thefirst component is electrically coupled to a current source, adjacent toa second component comprising a second metal or alloy and a second majorsurface, wherein the second component is electrically coupled to thecurrent source, to define a joint region between adjacent portions ofthe first major surface of the first component and the second majorsurface of the second component; introducing a metal or alloy powder toat least a portion of the joint region; controlling, by a controller, acurrent source to cause the current source to output an electric currentthat passes from the first component, through at least a portion of themetal or alloy powder, into the second component, wherein: the electriccurrent is an alternating current, and a frequency of the alternatingcurrent is configured to cause standing electromagnetic waves within atleast a portion of the particles of the metal or alloy powder.
 10. Themethod of claim 9, further comprising: controlling, by the controller,positions of a first electrode electrically coupled to the currentsource and the first component and a second electrode electricallycoupled to the current source and the second component relative to thefirst and second components, respectively.
 11. The method of claim 10,wherein at least one of the first electrode or the second electrode isconfigured to pass the electric current through a surface area greaterthan about sixteen square millimeters on the first major surface or thesecond major surface.
 12. The method of claim 9, wherein the frequencyof the alternating current is about 1 kHz to about 10 GHz.
 13. Themethod of claim 9, wherein the first metal or alloy is different thanthe second metal or alloy.
 14. The method of claim 9, wherein at leastone of the first component and the second component comprises a nickelbased superalloy or a titanium based alloy.
 15. The method of claim 9,wherein the metal or alloy powder comprises substantially the samecomposition as the first component, substantially the same compositionas the second component, or a composition comprising a blend of thecomposition of the first component and the composition of the secondcomponent.
 16. The method of claim 9, wherein the metal or alloy powderis substantially free of a melting point depressant.
 17. A controllerconfigured to pass an electric current from a current source into afirst component, through at least a portion of a metal or alloy powder,into a second component, wherein: the first component comprises a firstmetal or alloy and a first major surface, and is electrically coupled tothe current source; the second component comprises a second metal oralloy and a second major surface, and is electrically coupled to thecurrent source, the first major surface of the first component and thesecond major surface of the second component are positioned adjacent toeach other to define a joint region between adjacent portions of thefirst major surface of the first component and the second major surfaceof the second component; the metal or alloy powder disposed in at leasta portion of the joint region; the electric current is an alternatingcurrent; and a frequency of the alternating current is configured tocause standing electromagnetic waves within at least a portion of theparticles of the metal or alloy powder.
 18. The controller of claim 17further configured to control positions of a first electrodeelectrically coupled to the current source and the first component and asecond electrode electrically coupled to the current source and thesecond component relative to the first and second components,respectively.
 19. The controller of claim 17, wherein the frequency ofthe alternating current between about 1 kHz to about 10 GHz.
 20. Thecontroller of claim 17, wherein at least one of the first component andthe second component comprises a nickel based superalloy or a titaniumbased alloy.